The current application is a continuation-in-part application of U.S. application Ser. No. 10/822,228, filed Apr. 8, 2004, which is a continuation-in-part application of U.S. application Ser. No. 10/602,529, “Integrated-Circuit Implementation Of A Storage-Shelf Router And A Path Controller Card For Combined Use In High-Availability Mass-Storage-Device Shelves That May Be Incorporated Within Disk-Arrays,” herein incorporated in its entirety by reference, which is a continuation-in-part application of U.S. application Ser. No. 10/341,835. U.S. application Ser. No. 10/602,529 (“parent application”), which is a continuation-in-part application of U.S. application Ser. No. 10/341,835, includes extensive background information related to the storage-shelf router, path-controller cards, and high-availability storage shelf in which the described embodiment of the current invention is implemented. The parent application, in addition, includes extensive background information on fibre channel (“FC”), the small computer systems interface (“SCSI”), advanced technology attachment (“ATA”) disk drives, and serial ATA (“SATA”) disk drives.
FIG. 1 illustrates an exemplary, high availability, storage shelf. More detailed illustrations and descriptions are available in the parent application. In FIG. 1, a number of SATA disk drives 102-117 are located within a storage shelf. Each SATA disk drive is accessed via one or both of an x-fabric FC link 120 and a y-fabric FC link 122. Data and control information directed to the SATA disk drives by a disk array controller via the x-and-y-fabric FC links 120 and 122 are received by two storage-shelf-router cards (“SR card”) 124 and 126 and routed to individual SATA disk drives 102-117. The SR cards 124 and 126 receive data and command responses from the SATA disk drives 102-117 and transmit the data and command responses to a disk-array controller via the x-and-y FC links 120 and 122. In the exemplary storage shelf 100, each SR card 124 and 126 includes two integrated-circuit storage-shelf routers (“SRs”), with SR card 124 including SRs 128 and 130 and SR card 126 including SRs 132 and 134. Each SATA disk drive is interconnected via a single serial communications link to a path-controller card. For example, SATA disk drive 114 is interconnected via a single serial communications link 136 to a path-controller card (“PC card”) 138. The PC cards are each, in turn, interconnected with two SRs via two serial SATA links and two serial management links, discussed with reference to subsequent figures, below. The SRs 128, 130, 132, and 134 are each interconnected with one or more I2C buses through with the SRs can transmit asynchronous event notifications (“AENs”) to entities external to the storage-shelf via a SCSI enclosure services (“SES”) processor.
The high-availability storage shelf 100 illustrated in FIG. 1 employs embodiments of the SRs and PC cards that together represent embodiments of the invention disclosed in the parent application. As discussed, in detail, in the parent application, this exemplary high-availability storage shelf allows a large number of less expensive SATA disk drives to be incorporated within disk arrays designed to accommodate FC disk drives. The exemplary embodiment is but one of many possible embodiments of the invention disclosed in the parent application. A storage shelf may contain, for example, a single SR, multiple SRs that each reside on a single SR card, multiple SRs contained on a single SR card, and multiple SRs contained on each of multiple SR cards. Embodiments of the present invention are applicable to any of these storage-shelf embodiments.
An important problem that arises in using SATA disk drives within a FC-based disk array is that FC disk drives are dual ported, while SATA disk drives are single ported. A disk-array controller designed for an FC-based disk array expects disk drives to have redundant ports, so that each disk drive remains accessible despite a single-port or single-path failure. Disk-array and disk-array-component designers and manufacturers have recognized a need for an interconnection scheme and error-and-event detection, diagnosis, and handling methodologies to allow less expensive SATA disk drives to be incorporated within FC-based disk-arrays without extensive modification of FC-based disk-array controller implementations, SATA disk drives, and SATA disk-drive controllers.